Enamelware making



Patented Aug. 6, 1940 UNITED STATES PATENT OFFICE ENAMELWARE MAKINGJacob E. Rosenberg, Pittsburgh, Pa., assignor to Enamelers Guild, Inc.,a corporation of Pennsylvania No Drawing. Application July 13, 1939,Serial No. 284,246

. 3 Claims. This invention relates to the production of enamelware, and,specifically, to the production circumstances a skin apparently formsupon the air interface of the molten layer of coating, and

in the cooling and solidification of the layer the underlying body ofglass (it would seem) contracts slightly, with the effect of causing theskin to wrinkle and the wrinkles to organize 2 themselves into groupsradiating from centres that seem to be determined by chance. Theminutely waved surface, in the formation of which order and chance arecombined, under the light of day relieves monotony of appearance andimposes upon an otherwise plane surface a pattern that closely resemblesthe surface pattern of galvanized iron. The appearance is pleasing. Thissurface, finish has been called crinkle finish." I In the specificationof the earlier application named it has been said that coloring mattermay be included in the composition of the coating; that, ifcoloringmatter be present, it may not be itself a compound of reducing nature;for, if it is, the desired crinkle finish will not develop; And theinference is suggested, that the skin that forms upon the air interfaceof themolten layer of coating may be formed by oxidation.

A typical pigment of reducing nature is cadmium sulpho-selenide. It iswidely used in the enameling industry to produce a clear and brilliantred color. If cadmium sulpho-selenide be present as pigment in thecoating, although antimony trioxide in excess together with a fluoridebe present, still the crinkle finish will not develop.

This failure I impute to the activity of the selenide in taking upoxygen, and so preventing the formation of the skin of the hypothesis.

My present invention lies in a procedure that enables me to use pigmentsof reducing nature, and still to gain'thecrinklefinish. I resort to theexpedient of overspraying. I form the frit and prepare and apply theslip in usual manner,

including the desired pigment; and I prepare an overspray material thatincludes in its composition a fluoride together with an antimonycompound of trivalent character and that, when it has been fused andsolidified, is transparent or translucent. I apply the overspray to theout- 5 spread layer of pigmented coating (the layer may or may not havebeen preliminarily dried and baked), and I then fire the whole in anoxidizing atmosphere. In the firing, the overspray seals the pigmentfrom the access of air, the skin 10 forms, and in the cooling velops.

The overspray compounded according to the formula given in the Baldwinapplication alluded the crinkle finish deto above may be as follows:

Parts Dehydrated borax (NagB4O1) 15.4 Soda ash (Na2CO3) 6.5 Silica(SiO2) 23.8 m

Feldspar (NaK.OA12Os.6SiOz) 33.2 Cryolite (NasAlFe) 10.5 Fluorspar(CaFz) 4.3 Antimony trioxide (SbiOt) 8.5 Nitrate of soda (NaNOa); 3.2 35

In the smelting, while there is a small loss. in total weight, there isno loss in the weights of the cryolite and the antimony trioxideconstituents; and it will be found that in the frit these twoconstituents will continue-cryolite, substantially 10.5%, and antimonytrioxide, substantially 8.5%.

By varying the degree of translucency of the overspray the intensity ofcolor may be varied, and by including inthe overspray other pigment(having no reducing efiect) I may modify the color of th product.

- In the ensuingmlaims I shall use the term clear enamel in the sensethat is familiar in the industry, definitive of material which, sprayedupon and fired upon the otherwise prepared article, will afiord asurface layer that is lighttransmitting. 4

While it is true that in the enameling industry of today the onlypigment of reducing nature in general use, other than cadmiumsulphoselenide is cadmium sulphide (a pigment that gives an intenseyellow color to the ware), the invention is pertinent, in that case andin any other-case as well, in which a pigment of reducing nature isemployed.

It remains only to say that the industry knows how to develop within themolten substance of glass from other cadmium and selenium compounds theparticular pigments that I have named; and it will be understood that Imean to include in the field of practice 01 my invention such productionof pigment.

I claim as myinvention: I

1. The method herein described of producing an article of enamelware ofcrinkle finish which consists in spreading upon the surface-of thearticle to be enameled a vitreous coating that includes a pigment ofreducing nature, over- ,s'praying such coating with a coating of milledclear enamel that carries, in association with a fluoride, an antimonycompound of trivalent character, firing in an oxidizing atmosphere, and

cooling.

2. The method herein described of producing an article of enamelware ofcrinkle finish. which consists in spreading upon the surface or 'thearticle to be enameled a vitreous coating that iricludes as a pigmentcadmium sulpho selenide, 'overspraying .such coating with a coating ofmilled clear enamel that carries, in association with a fluoride, anantimony compound of trivalent character, firing in anoxidizingatmosphere,

and cooling.

3. The method herein described of producing an article of enamelware ofcrinkle finish which consists in spreading upon the surface of thearticle to be enameled a vitreous coating that

